So another big study comes up with a Relative Risk of miniscule size for exposure to air pollution.
My thanks to Peter Moffett MD for sending me this article. He knows I am interested in air pollution studies and he is the research director for our program so he is always reviewing the literature.
This is from Lancet Lancet 2014; 383: 785–95
Published Online
December 9, 2013
http://dx.doi.org/10.1016/
S0140-6736(13)62158-3
Effects of long-term exposure to air pollution on
natural-cause mortality: an analysis of 22 European cohorts
More than 40 authors In Europe. Lancet 2014; 383: 785–95
Published Online
December 9, 2013
http://dx.doi.org/10.1016/
S0140-6736(13)62158-3
Multicentre ESCAPE project
Summary
Background Few studies on long-term exposure to air pollution and mortality have been reported from Europe.
Within the multicentre European Study of Cohorts for Air Pollution Eff ects (ESCAPE), we aimed to investigate the
association between natural-cause mortality and long-term exposure to several air pollutants.
Methods We used data from 22 European cohort studies, which created a total study population of 367 251 participants.
All cohorts were general population samples, although some were restricted to one sex only. With a strictly
standardised protocol, we assessed residential exposure to air pollutants as annual average concentrations of
particulate matter (PM) with diameters of less than 2·5 μm (PM2·5), less than 10 μm (PM10), and between 10 μm and
2·5 μm (PMcoarse), PM2.5 absorbance, and annual average concentrations of nitrogen oxides (NO2 and NOx), with land
use regression models. We also investigated two traffi c intensity variables—traffi c intensity on the nearest road
(vehicles per day) and total traffi c load on all major roads within a 100 m buff er. We did cohort-specifi c statistical
analyses using confounder models with increasing adjustment for confounder variables, and Cox proportional
hazards models with a common protocol. We obtained pooled eff ect estimates through a random-eff ects metaanalysis.
Findings The total study population consisted of 367 251 participants who contributed 5 118 039 person-years at risk
(average follow-up 13·9 years), of whom 29 076 died from a natural cause during follow-up. A signifi cantly increased
hazard ratio (HR) for PM2·5 of 1·07 (95% CI 1·02–1·13) per 5 μg/m³ was recorded. No heterogeneity was noted
between individual cohort eff ect estimates (I² p value=0·95). HRs for PM2·5 remained signifi cantly raised even when
we included only participants exposed to pollutant concentrations lower than the European annual mean limit value
of 25 μg/m³ (HR 1·06, 95% CI 1·00–1·12) or below 20 μg/m³ (1·07, 1·01–1·13).
Interpretation Long-term exposure to fine particulate air pollution was associated with natural-cause mortality, even
within concentration ranges well below the present European annual mean limit value.
Funding European Community’s Seventh Framework Program (FP7/2007–2011).
I suppose you would wonder why I bolded the Hazard Ratios–well because this is an observational study with mortality rates as the endpoint and here they are again, claiming that a less than 10% increase in rate of deaths is proof of causation.
I need not point out that such a small association is always what these studies come up with, and it means nothing.